It is well known that conventional motor vehicle mufflers include a container defining an inner space or cavity that is filled with an acoustical insulation or damping material. Most often, the material is glass fiber material. The motor vehicle muffler is filled with the aid of pneumatic devices, which generally comprise heavy pipes and powerful fans.
U.S. Pat. No. 4,569,471, to Ingemansson et al., the disclosure of which is incorporated herein by reference, discloses a process and apparatus for feeding lengths of a continuous glass fiber strand into an outer shell of a muffler. The apparatus includes a texturizing device with a nozzle for expanding the continuous glass fiber strand into a wool-like material before the wool-like material enters the outer shell. In a first embodiment of the invention, the filling of an outer cylinder of the muffler outer shell occurs without an end-piece joined to the outer cylinder. After the filling operation is completed, the outer cylinder is moved to a separate station where the end piece is welded onto the outer cylinder. In a second embodiment of the invention, a perforated pipe/outer end piece assembly is located only part way in the outer cylinder during the filling operation. After the filling operation has been completed, the perforated pipe/outer end piece assembly is moved to its final position within the outer cylinder.
The aforementioned process is typically not used with clam shell mufflers comprising first and second halves which, when coupled together and enclosing a perforated pipe, may not have an open end through which insulation or damping material may be fed.
It is also known in the prior art to form preforms from glass fiber material which are adapted to be inserted into a first muffler shell section prior to its being coupled to a corresponding second muffler shell section. An example of a prior art preform is disclosed in U.S. Pat. No. 5,766,541, to Knutsson et al., the disclosure of which is incorporated herein by reference. While such preforms are acceptable in performance, they add additional cost to the muffler due to the manufacturing steps necessary to form the preforms.
It is also known to fill a mesh or bag with fibrous material. The mesh or bag is then inserted into a first muffler shell section prior to the first muffler shell section's being coupled to a second muffler shell section. An example of such a bag is disclosed in U.S. Pat. No. 6,068,082, to D'Amico, Jr. et al., the disclosure of which is incorporated herein by reference. Such bags are filled in a semi-automatic machine and then sealed by heat in a manual operation. To seal the bag after being filled, an operator has to make sure that no fibrous material (i.e., filaments) are present between the layers of the bag where the seal is to be made. Otherwise the seal may be compromised.
There is a need for an improved, low-cost process that can be used to fill a muffler shell.